Also i'm not sure if that would explain why I can get the keys to broadcast with two of my toons but not when the other three are the main
It would explain it, because all toons where it doesn't work Phort(LSHIFT+LCTRL+I), PHORC (LSHIFT+LALT+I) and PHORA (LSHIFT+LALT+ LCTRL + I) use shift in their modifiercombination, which identivies them.
So if shift+i would be bound to another action, the follow-macro which is on i would not get triggered.
Could you maybe check the keybinding-file for all toons if shift+i is realy unbound? -Or maybe post the macro you bound to i, for more helping/guessing?